Process for removing free fatty acids from fats and oils of biological origin or their steam distillates

ABSTRACT

To remove free fatty acids from fats or oils of biological origin or their steam distillates, it is proposed to extract the free fatty acids with a mixture of basic organic nitrogen compounds and water as extraction medium at a temperature below the boiling point of the organic nitrogen compounds. The content of the basic organic nitrogen compounds in the extraction medium shall be at least about 20% by weight and at most about 60% by weight, preferably between about 30% by weight and about 40% by weight. In this manner, the formation of a viscous soapstock which is difficult to remove is prevented. The boiling point of the basic organic nitrogen compound(s) used shall be the same as or above the boiling point of water and below the boiling point of the fatty acids to be extracted in order to enable simple recovery of the extraction medium.

[0001] The present invention relates to a process for removing freefatty acids from fats and oils of biological origin or their steamdistillates by extraction.

[0002] In human nutrition, and as raw materials for the chemicalindustry, oils and fats of biological origin play an important role. Forexample, they serve as raw materials for production of surfactants,plasticizers, waxes, lubricants, fatty alcohols etc. Essentialcomponents of fats and oils are the triesters of glycerides and fattyacids, the so-called triglycerides. The physical properties of fats andoils are determined a) by the chain length of the fatty acids, b) by thedegree of saturation of the fatty acids and c) by the distribution ofthe various fatty acids on the three hydroxyl groups of the glycerol.Fats having a high saturated fatty acid content are generally solid atambient temperature. Fats or oils, respectively, from predominantlyunsaturated fatty acids are liquid at ambient temperature.

[0003] The fats and oils of biological origin comprise a number ofsecondary products which adversely affect the keeping quality, odour,flavour and appearance. The most important secondary products are:suspended matter, organic phosphorus compounds, free fatty acids,pigments and odour compounds. Mucilaginous material (gums) and othercomplex colloidal compounds can promote hydrolytic degradation of fatsand oils during their storage and interfere during further refining.Therefore, they are removed by the process of what is termed degumming.Degumming is based on hydration with water or direct steam. The organicphosphorus compounds (phosphatides) take up water in the course of this,swell and become insoluble.

[0004] After phosphorus compounds and suspended matter have been removedby degumming and, if appropriate filtration, the further object is toseparate off free fatty acids and pigments and odour compounds.Commercial crude fats and crude oils comprise on average from 1 to 3% byweight of free fatty acids, high-grade types 0.5% by weight or less,some palm, olive and fish oils 20% by weight or more. The fatty acidcontent of the refined fats and oils is, by comparison, generally to bebelow 0.1% by weight. Whereas relatively long-chain free fatty acids donot usually cause flavour impairment, the short-chain fatty acids have asoapy, rancid flavour. In practice, the deacidification performed forremoving the free fatty acids is predominantly carried out by treatmentwith aqueous alkali solutions or by steaming at temperatures ofapproximately 220° C. Removing the free fatty acids by esterificationwith glycerol or a monohydric alcohol, by selective solvent extractionor by adsorbents, is of lower importance, by comparison. Below, thedeacidification processes known hitherto are described in more detail.

[0005] The treatment with alkaline solutions, as the method mostemployed, can be carried out batchwise or continuously. The higher thelye concentration, the more readily are unwanted accompanying substancestaken up into the resulting soap, termed the soapstock. Weakly alkalinesolutions are generally sprayed onto the oil at 90° C. and percolatedownwards through the heated oil. In contrast, stronger lyes (4 n to 7n) are usually stirred into the oil at from 40 to 80° C. After thedeacidification and removal of the soapstock, the oil or fat is washedwith highly dilute lye (approximately 0.5 n) and thereafter with water,in order to remove soap residues down to at least 0.05% by weight. Withthe use of centrifuges, a completely continuous plant for neutralizingfats and oils can be constructed according to this method. If the fatsand oils to be deacidified have a high content of free fatty acids, thedeacidification using alkaline solutions leads to a relatively hardsoapstock which can only be removed from the plant with difficulty.

[0006] Therefore, what is termed steam deacidification has beendeveloped as an alternative In this process, which is also termedphysical refining or deacidification by distillation, the free fattyacids are likewise continuously removed from the crude oils by hot steamunder vacuum. This process does not depend on the free fatty acids beingdistilled off completely, since fatty acids remaining in a small amountcan expediently be removed by a secondary lye refining. Before thedeacidification by distillation, the crude fat must, however, be freedas completely as possible from gums, phosphatides and metaltraces—usually by treatment with phosphoric acid—since the accompanyingsubstances can lead, during the distillation, to dark,unpleasant-tasting substances, which can then virtually no longer beremoved. The steam deacidification takes place at relatively hightemperatures; for example palm oil is deacidified by superheated directsteam at 220° C. The high temperature destroys a great number ofsubstances which are present in the oil (or fat) and are desirable perse, for example the antioxidants which improve the keeping quality ofthe oil, or forces these substances into what is termed the steamdistillate which is produced after condensation of the superheated steamused for the deacidification.

[0007] The neutralization of oils and fats by separating off the freefatty acids from the crude fat by means of selective solvents is anothermethod which is suitable, especially, for high-acidity oils and fats.For example, liquid extraction using ethanol makes possible thedeacidification of olive oil having 22% by weight of free fatty acidsdown to approximately 3% by weight of free fatty acids. Anotherextraction medium which dissolves, at suitable temperatures, only freefatty acids and very highly unsaturated triglycerides, is furfural. Inyet another process, the Selexol process, liquid propane is used asextraction medium in countercurrent. Liquid propane selectivelydissolves saturated neutral oil, while fatty acids, oxidation products,unsaponifiables and highly unsaturated glycerides are hardly dissolvedat all and remain behind. This process is chiefly used for fractionatingfish oils and fish liver oils.

[0008] The selective extraction process is used industrially virtuallyexclusively for fats having a very high free fatty acid content.Examples of these are: cocoa butter from shells, olive oil from thepress cake, low quality grades of rice oil and cottonseed oil. Thealcohol used in this process is isopropyl alcohol. To deacidify one tonof oil, Bernardini (E. Bernardini, Oilseeds, Oils and fats, PublishingHouse Rome, 1985) quotes the following levels of consumption: energy andauxiliaries, steam 800 kg, electrical energy 14 kWh, hexane 15 kg,isopropanol 18 kg. Oil produced in this manner is not used as edibleoil.

[0009] Although the degumming and alkali refining already lead to acertain clearing, generally, a decolourizing stage is further provided.Decolourizing is customarily performed using solid adsorbents, such asbleaching earth and activated carbon. Bleaching with air or chemicalsplays a minor role in edible fats.

[0010] In the last phase of the refining process, odour and flavoursubstances are removed from the deacidified and bleached oils and fats.Deodorization is essentially a steam distillation in which the volatilecompounds are separated off from the non-volatile glycerides. The odourand flavour substances are predominantly aldehydes and ketones which areformed by autoxidative or hydrolytic reactions during the processing andstorage of the fats and oils. The low partial pressure of the compoundsto be removed requires that the steaming is carried out under reducedpressure. Steaming is usually carried out from 180 to 220° C. and apressure of from 6 to 22 mbar.

[0011] For environmental protection reasons, wastewaters from thealkaline deacidification must be carefully treated, which is associatedwith costs. Therefore, most recently, the interest in physical processesfor refining oils and fats has been revived. As early as in the 1920s,the possibilities of deacidification using liquid-liquid extraction withaqueous lower alcohols were studied (Baley, 5th edition 1996, volume 5).The best extraction medium was found to be aqueous ethyl alcohol.Although in its selectivity with respect to free fatty acids andtriglycerides, pure methanol is more expedient, it has not been studiedin more detail for its suitability as an extraction medium fordeacidifying fats and oils—presumably because of its toxicity.

[0012] Deacidifying oils and fats using amines was proposed as early as1937 in U.S. Pat. No. 2,164,012. An alkanolamine, preferablyethanolamine, is proposed as alkaline extraction medium which dissolvesthe free fatty acids as soaps in the aqueous phase. Alkanolamineresidues dissolved in the raffinate are extracted by washing with dilutesulphuric acid, acetic acid, lactic acid, citric acid or hydrochloricacid solutions.

[0013] U.S. Pat. 2,157,882 likewise proposes, instead of extracting thefree fatty acids with sodium hydroxide solution, extracting with analkanolamine to remove the majority of the free fatty acids and some ofthe pigments. However, the oil thus treated is cloudy and has a tendencyto decompose during storage. Therefore, it is proposed to follow thewash with ethanolamine by a wash with a dilute sodium hydroxidesolution. The deacidified oil is thereafter washed with water, in orderto remove the last traces of alkali.

[0014] In an article which appeared in 1955 in Journal of the AmericanOil Chemist's Society (JAOCS, vol. 32, 1955 pp. 561-564), experiments onrefining rice oil with monoethanolamine, triethanolamine,tetraethanolammonium hydride, ethylenediamine, ethylamine andtriethylamine are reported. Rice oils comprise approximately from 5 to7% by weight of free fatty acids. The high fatty acid content usuallyleads, in alkaline refining, to high fat losses. These losses can bedecreased to values of from 3 to 5% by weight by adding the said aminesprior to the customary refining.

[0015] As can be seen by the above description of the variousdeacidification processes, these processes are either burdened withplant-engineering problems and/or are relatively cost-intensive, due totheir consumption of auxiliaries and energy and a downstream work-upwhich may be required. In addition, in some processes, fat and oilconstituents which are wanted per se are destroyed.

[0016] The object therefore underlying the invention is to specify animproved process for deacidifying oils and fats of biological originwhich, firstly, can overcome even high contents of free fatty acidswithout plant-engineering problems and, secondly, enables the productionof very high-quality grade fats and oils, as are wanted, for example, bythe food industry.

[0017] This object is achieved according to the invention by the processspecified in Patent claim 1. The process of the invention is based onthe fact that, surprisingly, when oils (or fats) having a high freefatty acid content are deacidified by aqueous solutions or organicbases, for example 2-dimethylaminoethanol, no viscous soapstock forms ifthe amine content in the aqueous solution is high. Instead, under suchconditions, both the oil phase and the extract phase are low-viscosityliquids. The phase separation proceeds in this case rapidly within a fewminutes; the resulting phases are clear.

[0018] In contrast, at aqueous solution amine contents which correspondto the concentrations of the sodium hydroxide solutions in the chemicaldeacidification, a high-viscosity soapstock formed. More detailed studyfound that the basic nitrogen compound must contain at leastapproximately 40% by weight of water so that two phases are formed inequilibrium with the oil to be deacidified. Conversely, theconcentration of the organic base, for example 2-dimethylaminoethanol,in the aqueous solution must be at least approximately 20% by weight,even better 30 to 40% by weight so that no viscous soapstock or cloudyphases are formed. This means that the aqueous solution used for thedeacidification must have according to the invention a content ofapproximately from 20% by weight to about 60% by weight of organicnitrogen compound.

[0019] If, for example, palm oil having a free fatty acid content of4.5% by weight is mixed at 50° C. with a solution of 55% by weight of2-dimethylaminoethanol in water in a ratio of 1:1, after separating thephases an oil is obtained which, minus the extraction medium, comprisesonly 0.03% by weight of free fatty acids at an oil loss of merely 0.8%by weight. By means of the extraction process of the invention, amild-temperature and efficient deacidification is thus possible at lowoil losses in a few stages in countercurrent.

[0020] Residues of the basic nitrogen compounds dissolved in theraffinate are preferably extracted with water or with dilute aceticacid, lactic acid, citric acid, sulphuric acid or hydrochloric acidsolutions. Alternatively, traces of the basic extraction medium in theraffinate are removed by stripping with carbon dioxide. During thestripping with carbon dioxide, at the same time, the oil is dried. Thecarbon dioxide can be used as dilute gas or as dense, supercritical gasfor removing traces of the basic nitrogen compounds used from theraffinate.

[0021] Extraction of the extraction medium used according to theinvention (for example an aqueous solution of 2-dimethylaminoethanol)from the extract may be performed in a simple manner by distillation. Itis a precondition here that the vapour pressure of the water isapproximately equal to or above the vapour pressure of the basicnitrogen compound(s) used. The water and the basic organic compound aredistilled off together or the water is preferably distilled off first,the ratio of basic compounds to water being constant or increasing andthe formation of a viscous soapstock being avoided. If the vapourpressure of the basic compound were to be higher than the water vapourpressure, the ratio of basic compound to water would decrease andfinally a viscous soapstock would begin to form. In other words, theboiling point of the basic nitrogen compound(s) has to firstly be equalto or above the boiling point of water and secondly must be below theboiling point of the fatty acids to be extracted.

[0022] Suitable basic organic compounds for the process of thisinvention should have the following properties: a) the compound shall,if possible, not form amides with the free fatty acids; b) the compoundshall be miscible with water in any ratio; c) the boiling point of thecompound shall be equal to or above that of water, d) the odour nuisancedue to the aqueous solutions shall be as small as possible. Examples ofsuitable organic nitrogen compounds are: N-methylmorpholine,2-dimethylaminoethanol, 3-(diethylamino)-1-propanol,2-diethylaminoethanol, 1-(dimethylamino)-2-propanol, dimethylformamide,N-methylmorpholine, 2-methylethylaminoethanol, 2-dibutylaminoethanol,dimethylformamide, morpholine, 2-diisopropylaminoethanol, etc. Ingeneral, tertiary amines, because of their higher basicity, arepreferred to binary and monosubstituted amines.

[0023] Examples of starting materials which can readily be deacidifiedby the process of the invention are beef tallow, lard, fish oil, cornoil, rendered fats, palm oil, soy oil, rapeseed oil, sunflower seed oil,rice germ oil, cotton seed oil, olive oil, groundnut oil, safflower oil,coconut oil, palm kernel oil, grape-seed oil, wheat germ oil etc. Beforethe process of the invention is used, the oils and fats to bedeacidified should be degummed and filtered, in particular if more than100 ppm of phosphatides are present. The fat or oil thus prepared stillcontains dissolved oxygen which should likewise be removed beforefurther processing. By means of the process according to the invention,the starting material is then deacidified with preservation oftemperature-sensitive compounds, such as carotenes, tocotrienols,tocopherols etc. These compounds, which are, inter alia, also ofnutritional importance, are largely destroyed or expelled duringconventional physical refining which is carried out by means of directsteam, owing to the high temperatures.

[0024] In a somewhat modified form, the process according to theinvention is also outstandingly suitable for removing the free fattyacids from the steam distillates of the fats and oils which have beendeacidified using the abovementioned conventional physical refining,i.e. by steam deacidification.

[0025] These steam distillates generally comprise free fatty acids atvery high concentrations, generally in the range from about 80 to 94% byweight. Because of the high free fatty acid content, the extractionmedium used according to the invention, i.e. the mixture of organic baseand water, must however be richer in the basic nitrogen compound thandescribed above in connection with the deacidification of fats and oils.The content of organic nitrogen compound in the extraction medium shouldbe at least approximately 40% by weight. If such abasic-nitrogen-compound-rich aqueous solution, for example 60% by weightof 2-dimethylaminoethanol and 40% by weight of water, is added to theliquid steam distillate as extraction medium, a liquid homogeneousmixture is obtained. To this liquid mixture are then added from one tofour parts, preferably from two to four parts, of an alkane and/or anester, in particular an acetate, to one part of liquid mixture. From thepreviously homogeneous mixture, as a result, two coexisting liquidphases are formed of which the aqueous phase highly selectively containsthe free fatty acids.

[0026] In the alkane and/or ester phase are dissolved essentially thefats and oils present in the steam distillate. The secondary productsalso dissolved in the steam distillate, such as tocopherols,tocotrienols and phytosterols, likewise pass highly selectively overinto the alkane phase. The aqueous phase having the free fatty acidspresent therein is of low viscosity, so that phase separation isperformed approximately within 20 minutes after interrupting the mixing.

[0027] The raffinate (alkane phase or ester phase) resulting afterseparating off the aqueous phase is, depending on the starting product,highly enriched in secondary products such as tocopherols, phytosterols,tocotrienols. Producing these valuable secondary products from suchconcentrates is possible under economically attractive conditions.

[0028] Suitable alkanes are, for example, propane, butane, hexane,petroleum ether, heptane, heptane fractions, octane etc. When butane orpropane is used as solvent for the formation of two phases, the pressurein the mixing vessel must at least correspond to the respective vapourpressure, so that the butane or propane is present in liquid form.Suitable esters are, in particular, the acetates, for example ethylacetate, propyl acetate, butyl acetate or a mixture thereof.

[0029] In the process according to the invention, if the free fatty acidconcentration in the starting material to be treated (oil, fat or steamcondensate) is more than approximately 50% by weight, the addition ofalkanes is generally required for the overall system (starting materialand extraction medium) to remain in two phases. The addition of alkaneor ester therefore, even at high free fatty acid concentrations in thestarting mixture, ensures the formation of two easily handled liquidphases, and by means of the extraction medium used according to theinvention, by an extraction in countercurrent, extracts having high freefatty acid concentrations can be obtained. The solvent ratio cantherefore be low, which has an advantageous effect on the economicefficiency of the process according to the invention.

[0030] An embodiment of the process according to the invention isdescribed in more detail with reference to the single FIGURE showing aprocess flow chart.

[0031] Via a line 10, a starting product (oil, fat or steam distillate)is fed to a first extraction tower 12. In the extraction tower 12, thefree fatty acids are highly selectively extracted from the startingproduct with an extraction medium which consists of a mixture of a basicnitrogen compound and water. The extraction medium used comprises atleast approximately 20% by weight and at most 80% by weight of theorganic nitrogen compound (organic base). Particularly favourable provedconcentrations of the basic nitrogen compound of approximately 30 to 40%by weight. But the basic nitrogen compound concentration may as well bechosen to be even higher.

[0032] The oil or fat freed from the free fatty acids is fed via a line14 to a wash tower 16 (extraction tower), in which residues of the basicnitrogen compound are washed out with water or an aqueous solution whichcomprises an acid, and leaves the wash tower 16 as raffinate R. The washsolution exiting at the top of the wash tower 16 via a line 18 is thenworked up by distillation in a distillation tower 20. During this, waterand, if appropriate, the volatile acid (for example acetic acid)dissolved in the water is distilled off until the bottom product of thedistillation tower 20 has reached the composition of the extractionmedium. This bottom product is then passed via a line 22 to theextraction medium cycle described below, while the distillate of thedistillation tower 20 is fed as wash liquid via a line 24 to theabovementioned wash tower 16.

[0033] The extraction medium which comprises the free fatty acids and istaken off at the top of the extraction tower 12 is fed via a line 26 toa second distillation tower 28. Water and the basic nitrogen compoundare produced as overhead product during the distillation in thedistillation tower 28, while the extract comprising the extracted freefatty acids and some neutral oil is taken off as bottom product from thedistillation tower 28 via a line 30. The overhead product of thedistillation tower 28 is fed as extraction medium via a line 32 to theextraction tower 12 in which the extraction of the free fatty acidstakes place, which completes the extraction medium cycle. The energyrequired for the distillation is fed in the form of heating steam vialines 34 and 36 to the distillation towers 20 and 28.

[0034] In this manner, by extraction, an acid-free oil or fat isproduced as raffinate and the extracted free fatty acids, which stillcomprise small amounts of neutral oil, are produced, in a closed circuitof all auxiliaries. No waste streams are formed. Secondary products, forexample tocopherols, tocotrienols, carotenes, phytosterols,cholesterols, etc., which are present in the starting product remain inthe raffinate R.

[0035] A number of experiments, which are described below, were carriedout using the process according to the invention.

EXAMPLE 1

[0036] 250 g of an oil comprising 95.5% by weight of neutral oil, 4.2%by weight of free fatty acids and 1.7% by weight of tocopherol weremixed with 100 g of 2-dimethylaminoethanol and 70 g of water at 50° C.by stirring. After interrupting the mixing operation and separating thetwo liquid phases, samples were taken from both phases and analysed. Theextraction-medium-rich phase comprised, minus extraction medium, 53.7%by weight of neutral oil, 45.0% by weight of free fatty acids and 0.3%by weight of tocopherol. The oil-rich raffinate phase comprised, minusextraction medium, 98.2% by weight of neutral oil, 0.05% by weight offree fatty acids and 1.8% by weight of tocopherol.

EXAMPLE 2

[0037] 200 g of an oil comprising 5.5% by weight of free fatty acids and1.8% by weight of tocopherols were mixed at 50° C. with 150 g of anextraction medium which comprised 40% by weight of water and 60% byweight of 2-dimethylaminoethanol. After interrupting the mixingoperation and phase separation, one sample was taken from each of thetwo coexisting liquid phases and analysed. The extract phase had aloading of 8.9% by weight. Minus the extraction medium, the extractconsisted of 92% by weight of free fatty acids, 0.3% by weight oftocopherols and 7.7% by weight of glycerides. The raffinate phasecomprised, minus the extraction medium, 0.05% by weight of free fattyacids, 1.8% by weight of tocopherol and 98.2% by weight of glycerides.

EXAMPLE 3

[0038] 200 g of an oil having 5.1% by weight of free fatty acids and0.3% by weight of tocopherols was mixed with an extraction mediumconsisting of 100 g water and 100 g pyridin at 60° C. After interruptingthe mixing operation and phase separation, one sample was taken fromeach of the two coexisting liquid phases and analysed. The extract phasehad a loading of 2.1% by weight. Minus the extraction medium, theextract comprised 20.8% by weight of free fatty acids, 0.3% by weight oftocopherol and 95.8% by weight of glycerides. The raffinate comprised,minus the extraction medium, 4.2% by weight of free fatty acids, 0.3% byweight of tocopherols and 95.1% by weight of glycerides.

EXAMPLE 4

[0039] 151 g of an oil having a composition of 4.3% by weight of freefatty acids, 1.4% by weight of tocopherol, 0.6% by weight ofstigmasterol and 93.7% by weight of neutral oil were mixed at 50° C.with 150 g of an extraction medium comprising 60% by weight of2-(dimethylamino)ethanol and 40% by weight of water. After terminatingthe mixing operation, two phases were produced in the course of about 10minutes. After removing a slight turbidity by centrifugation, sampleswere taken from both phases and analysed. The extract phase, minus theextraction medium, had the following composition: 84% by weight of freefatty acids, 0.5% by weight of tocopherol, 0.5% by weight ofstigmasterol and 15% by weight of neutral oil. The raffinate comprised0.05% by weight of free fatty acids, 1.4% by weight of tocopherol, 0.6%by weight of stigmasterol and 97.95% by weight of neutral oil. In theextract there remained 0.46% by weight of the initial amount of neutraloil.

EXAMPLE 5

[0040] 300 g of palm oil having a content of 4.5% by weight of freefatty acids, 0.4% by weight of tocols, 0.15% by weight of stigmasterol,94.95% by weight of neutral oil were mixed at 50° C. with 42 g of anextraction medium which comprised 60% by weight of2-(dimethylamino)ethanol and 40% by weight of water. After terminatingthe mixing operation and phase separation, which lasted for about 35minutes, samples were taken from both phases and analysed. The extractcomprised, minus the extraction medium, 40.0% by weight of free fattyacids, 0.4% by weight of tocopherols, 0.25% by weight of stigmasteroland 59.35% by weight of neutral oil. The raffinate consisted, minusextraction medium, of 0.3% by weight of free fatty acids, 0.4% by weightof tocopherols, 0.1% by weight of stigmasterol and 99.4% by weight ofneutral oil. 6% by weight of the initial amount of neutral oil werepresent in the extract. The solvent ratio had the low value of 0.14.

EXAMPLE 6

[0041] 100 g of palm oil having a free fatty acid content of 5.5% byweight were mixed with 100 g of a mixture of 30 gN,N-dimethylamino-ethanol and 70 g water by stirring at 60° C. Afterinterrupting the mixing operation, the phase separation which had takenplace after approximately 3 minutes was waited for and samples weretaken from both coexisting liquid phases and analysed. The palm oil(raffinate) contained, minus extraction medium, less than 0.1% by weightof free fatty acids. The extract comprised, minus extraction medium, 77%by weight of free fatty acids and 23% by weight of glycerides (mono-,di- and triglycerides; the latter the main component). Approximately 1.2g glycerides (about 1.2% of the weighed sample) were extracted togetherwith the free fatty acids.

EXAMPLE 7

[0042] 100 g of palm oil with 4.3% by weight of free fatty acids weremixed at 80° C. with a solution consisting of 40% by weight ofN,N-dimethylamino-ethanol in water by stirring. After separating thecoexisting phases, samples were taken from each one of the phases andanalysed. The extract comprised, minus extraction medium, of 67% byweight of free fatty acids and 33% by weight of glycerides (mono-, di-and triglycerides). The raffinate comprised, minus extraction medium,less than 0.1% of free fatty acids. 2 g glycerides (about 2% of theweighed sample) were in the extract. 1.9% by weight ofN,N-dimethylamino-ethanol were dissolved in the raffinate which werewashed out with water.

EXAMPLE 8

[0043] 100 g of palm oil having a content of 4.2% by weight of freefatty acids were extracted at 50° C. with 100 g of a solution of 40% byweight of N,N-dimethylamino-ethanol in water. The extract comprised,minus extraction medium, 75% by weight of fatty acids and 25% by weightof glycerides. In addition to 3.1 g of fatty acids, the extract alsocomprises 1 g of glycerides (corresponding to a loss of fat of 1%). Theraffinate contained 0.1% by weight of fatty acids.

EXAMPLE 9

[0044] 200 g of a steam distillate comprising 92% of free fatty acidsand 0.19% of secondary components(tocopherols+tocotrienols+phytosterines) are dissolved in 400 g heptanefraction at 40° C. The solution is extracted with 600 g of a solution of40% N,N-dimethylamino-ethanol in water at 40° C. Two clear coexistingphases forming within a few minutes result. The extract (what has beendissolved in the extraction medium) comprises, minus extraction medium,96% of fatty acids. The raffinate comprises, minus extraction medium,13.4 g of glycerides, 0.7 g of free fatty acids, and 0.3 g of secondarycomponents (2% tocopherols+tocotrienols+phytosterines).

EXAMPLE 10

[0045] In a plant according to the accompanying FIGURE, palm oil was fedinto the first extraction tower 12 at a rate of 30.0 kg/h. Since thepalm oil comprised 4.3% by weight of free fatty acids, the feed via theline 10 consisted of 28.71 kg/h of neutral oil and 1.29 kg/h of freefatty acids. In the extraction tower 12, the palm oil was brought intocontact at 80° C. with 30.0 kg/h of extraction medium in countercurrent.The extraction medium was composed of dimethylaminoethanol (DMAE) andwater in a ratio of 1:1. The raffinate stream leaving the extractiontower 12 comprised 24.424 kg/h of neutral oil, 0.090 kg/h of free fattyacids, 0.855 kg/h of DMAE and 0.855 kg/h of water. The extract streamwas composed of 14.145 kg/h of DMAE, 14.145 kg/h of water, 0.285 kg/h ofneutral oil and 1.20 kg/h of free fatty acids.

[0046] The raffinate stream was fed to the wash tower 16, in which theDMAE was extracted from it at 80° C. with 15.0 kg/h of water incountercurrent. The raffinate stream thus purified left the wash tower16 in the following composition: 28.424 kg/h of neutral oil, 0.012 kg/hof DMAE and less than 0.025 kg/h of free fatty acids. This is equivalentto a neutral oil containing 0.00042 % by weight of DMAE and less than0.00088% by weight of free fatty acids. The wash water left the washcolumn 16 with the following composition: 15.855 kg/h of water, 0.855kg/h of DMAE and 0.064 kg/h of free fatty acids. The wash water wasregenerated in the distillation tower 20 at 100° C. As overhead product,15.0 kg/h of water was recirculated via the line 24 to the wash tower16. The bottom product containing 0.855 kg/h of water and 0.855 kg/h ofDMAE is combined with the extract stream from the extraction tower 12flowing through the line 26.

[0047] The extract stream from the extraction tower 12 combined with thebottom product from the distillation tower 20 was fed to thedistillation tower 28. The overhead product of the distillation tower 28of 15.0 kg/h of water and 15.0 kg/h of DMAE was recirculated asextraction medium via the line 32 into the extraction tower 12. Asbottom product, 0.285 kg/h of neutral oil and 1.264 kg/h of free fattyacids left the distillation tower 28. The extract therefore consisted of18.4% by weight of neutral oil and 81.6% by weight of free fatty acids.

[0048] The extraction medium cycle is thus closed, and there are nowaste elimination problems.

1. A process for removing free fatty acids from fats or oils ofbiological origin by extracting the free fatty acids with a mixture ofbasic organic nitrogen compounds and water as extraction medium at atemperature below the boiling point of the organic nitrogen compounds,where the content of the basic organic nitrogen compounds in theextraction medium is at least about 20% by weight and at most about 60%by weight, preferably between about 30% by weight and about 40% byweight, and the boiling point of the basic organic nitrogen compound(s)used is equal to or above the boiling point of water and below theboiling point of the fatty acids to be extracted.
 2. The processaccording to claim 1, characterised in that the basic nitrogencompound(s) in the refined fat or oil obtained by the extraction is/areextracted by means of water or aqueous solutions of volatile acids. 3.The process according to claim 1 or 2, characterised in that, when fatsand oils having a free fatty acid content of about 50% by weight or moreare being deacidified, alkanes and/or an ester, in particular anacetate, are added to the starting materials to be deacidified in aconcentration which is sufficient for the system of extraction medium,alkane and starting material to divide into two phases.
 4. The processfor removing free fatty acids from steam distillates of fats or oils ofbiological origin having the steps: extracting the free fatty acids witha mixture of basic organic nitrogen compounds and water as extractionmedium at a temperature below the boiling point of the organic nitrogencompounds, where the content of the basic organic nitrogen compounds inthe extraction medium is at least about 40% by weight and at most about60% by weight, preferably about 50% by weight or more, and the boilingpoint of the basic organic nitrogen compound(s) used is equal to orabove the boiling point of water and below the boiling point of thefatty acids to be extracted and adding from 1 to 4 parts, preferablyfrom 2 to 4 parts, of alkane and/or of an ester, in particular anacetate, to 1 part of the liquid homogeneous mixture obtained in thepreceding extraction step.
 5. The process according to claim 3 or 4,characterised in that the basic nitrogen compound(s) in the alkane phaseand/or ester phase is/are extracted by means of water or aqueoussolutions of volatile acids.
 6. The process according to one of claims 2or 5, characterised in that the organic nitrogen compound(s) dissolvedin the water or the aqueous solution of volatile acids after theextraction step is/are separated off by distillation.
 7. The processaccording to one of claims 3 to 6, characterized in that the alkane usedis propane, butane, pentane, hexane, heptane, heptane fraction, octaneor a mixture thereof.
 8. The process according to one of claims 3 to 7,characterised in that the ester used is ethyl acetate, propyl acetate,butyl acetate or a mixture thereof.
 9. The process according to one ofthe preceding claims, characterised in that the extracted fatty acidsare separated off from the extraction medium by distillation atatmospheric pressure or reduced pressure of the extraction mediumcomprising the fatty acids.
 10. The process according to one of thepreceding claims, characterised in that the basic organic nitrogencompound used is tertiary amines.
 11. The process according to one ofthe preceding claims, characterised in that the basic organic nitrogencompound used is 2-dimethylaminoethanol, 2-methylaminodiethanol,4-methylmorpholine, 2-diisopropylaminoethanol, 2-dibutylaminoethanol,3-Dimethylaminopropanol, 1-dimethylamino-2-propanol,2-dimethylaminoethanol, 2-methylamino-1-butanol,2-(methylethylamino)ethanol, dimethylformamide, morpholine, pyridine,2-dimethylamino-2-methyl-1-propanol, 4-methylpyridine, 1-methylpyrrole,2-dibutylaminoethanol, 2-dimethylaminoethylamine, monoethanolamine,3-dimethylamino-1-propanol, dimethylamino-2-propanone,1-dimethylamino-1-propylenamine, or a mixture of these compounds.